The present invention pertains to a cutting insert to be used in cutting tools during machining operations. More particularly, the present invention relates to an insert having a convex wiper cutting edge defined between two surfaces wherein one of the surfaces is a clearance face having a positive clearance angle.
It is well known to provide cutting inserts with wiper cutting edges by creating a straight edge or facet on the insert cutting edge. This facet is located after the major cutting edge and creates an improved surface finish by reducing the magnitude of the high points on the machined surface.
When creating a straight edge or facet on the insert cutting edge, the width of the facet must be greater than the advance per revolution to allow the cutting edges to overlap. Moreover, the spindle must be tilted at a critical angle because excessive spindle tilt causes the insert to dig into the work surface due to the sharp ends on the insert. Thus, this configuration does not allow for the rotational angular tolerance of the insert when mounted in the insert pocket.
This design has been improved upon by grinding the side surface of the facet so that it is radiused, thereby creating a radiused wiper cutting edge. The ground radius allows for the angular tolerance without having a detrimental effect on the resulting surface finish by insuring that the ends of the cutting edge do not contact and scratch the work surface.
Instead of grinding the side surface of the facet, the radius on the wiper cutting edge can be formed by grinding the top, chip breaking surface of the insert. An example of such an insert is the MICRO MILL insert available from Ingersoll as Part No. YCE434-01. However, this type of insert requires a negative axial rake to produce the convex wiper cutting edge. In addition, the grinding of the top surface and the accuracy with which it is ground create additional manufacturing operations and costs. Thus, it would be desirable to provide an insert having a generated convex cutting edge (wiper), or a convex cutting edge (wiper) that is formed without grinding.
The present invention is directed towards a cutting insert comprising a rake face including a convex portion, a flank face including a clearance face having a positive clearance angle, a cutting edge formed at an intersection between the rake face and the flank face, and a convex cutting edge formed on the cutting edge.
The invention is also directed towards a method for forming a cutting insert. The method comprises the steps of placing a powdered material into a die and pressing the powdered material in the die to achieve a form having a convex rake face and at least one flank face including a clearance face having a positive clearance angle. Next, the form is removed from the die and sintered.